In July 1980, the Tower Chemical Company let massive amounts of toxic and endocrine-disrupting chemicals (EDCs) spill into Lake Apopka in central Florida. We are studying the alligator population in Lake Apopka to understand how reproductive systems function in the face of overwhelming endocrine disruption.
Today, Lake Apopka is classified as a Superfund site by the US government and considered Florida’s most polluted large lake.
DDT (dichloro-diphenyl-trichloroethane) was developed in the 1940s as a synthetic insecticide. It was initially used to fight malaria, typhus, and the other insect-borne human diseases.
In the 1950s and 60s, however, scientists began to document the chemical’s environmental and toxicological effects. The publication of Rachel Carson's Silent Spring in 1962 generated widespread concerns over DDT use.
In 1972, the EPA issued a cancellation order for DDT, but studies have continued to document the relationships between DDT exposure and reproductive failure.
When ingested, DDT acts as an endocrine-disruptor, meaning that it binds to estrogen and/or progesterone receptors in the body.
When that happens, DDT messes with hormonal regulation, including hormone synthesis; hormone release and storage; hormone transport and clearance; the thyroid function; the central nervous system; and more.
Since DDT contamination, the alligator population of Lake Apopka has continued to produced spermless males, "intersexed" gators with testes and ovaries, and females that lay huge clutches of dead eggs.
In 1929, August Krogh published the simple but striking observation that extreme phenotypes provide a unique opportunity to study human-relevant problems. This is particularly true when the extreme phenotype mirrors a human disease or provides otherwise unfeasible study approaches.
More than 80 years after Krogh’s Principle, there remains a surprising disconnect between evolutionary and medical biology. The alligators of Lake Apopka offer a unique opportunity to use anthropogenic selection as a tool to inform our understanding of reproductive disorders.
